Method of casting

ABSTRACT

This invention relates to a founding process involving metal alloy compositions which upon solidification precipitate at least two distinct phases simultaneously. The metallurgical structure of castings resulting from this founding process is altered by subjecting the solidifying metal to a mild angular or rotative acceleration. The direction of this angular acceleration is periodically reversed to avoid high rotational speeds. This results in an angular or rotative oscillation.

Related US. Application Data Continuation-impart of Ser. No. 760,126, Sept. 13, 1968, Pat. No. 3,614,976.

US. Cl 164/114, 164/122, 164/260 Int. Cl. B22d 13/00 Field of Search 164/71, 83, 114-116,

References Cited UNITED STATES PATENTS 12/1911 Bruckmann 164/260 10/1912 Crawford 164/115 United States Patent 1 [1 3,741,279

( Iole et al. June 26, 1973 METHOD OF CASTING 2,116,367 5/1938 Smith 164/260 x [76] Inventors: Gerald s. Cole, 4839 Middlesex, 333 2;; H Dearborn, Mich. 48126; Gustaf F. u

Bolling, 24646 Winona Drive, FOREIGN PATENTS OR APPLICATIONS Dearbom, Mich- 48124 399,331 10/1933 Great Britain 164/71 [22] Filed: Oct. 4, 1971 I pp No: 186,336 Pnmary ExammerR. Spencer Annear AttorneyKeith L. Zerschling et al.

[5 7] ABSTRACT This invention relates to a founding process involving metal alloy compositions which upon solidification precipitate at least two distinct phases simultaneously. The metallurgical structure of castings resulting from this founding process is altered by subjecting the solidifying metal to a mild angular or rotative acceleration. The direction of this angular acceleration is periodically reversed to avoid high rotational speeds. This results in an angular or rotative oscillation.

4 Claims, 5 Drawing Figures OJC/LZATED PATENTED JUN 26 ms SllEEI-SUFS PAIENIED JUNZB I975 'SHEETUUFS F'IG.4

.' ROTAT ED 'SScILLATED STATIC DISTANCE FROM INGOT EDGE INGOT EDGE INGOT CENTER (INCHES) QUANTITATIVE METALLOGRAPHIC ANALYSIS OF PERCENT GRAPHITE IN A 4.|C, l.6S'| GREY CAST IRON.

PATENIEDJUNZG ms SIIEEI S IIF 5 FIG.5

TRW VI A ALLOY LO 7 2.0 A DISTANCE FROM LEADING EDGE OF BLADE (INCHES) QUANTITATIVE METALLOGRAPHIC ANALYSIS OF PERCENT GAMMA PRIME IN TWO NICKEL-BASE SUPERALLOYS METHOD OF CASTING This invention is a continuation in part of Application Ser. No. 760,126 filed Sept. 13, 1968 and now U.S. Pat. No. 3,614,976 issued Oct. 26, 1971.

THE INVENTION The origins of the founding art are lost in the mists of time and it has long been known that the final properties of castings are strongly influenced by the combined effects of many gross factors and also by many subtle factors such as metal composition, melting conditions, degree of superheat, inoculation, mold composition and rate of cooling. These sundry and subtle variables have been manipulated in many ways to obtain the desired final properties.

This invention is predicated upon our discovery that the metallurgical characteristics of castings which precipitate at least two distinct phases upon solidification can be decidedly improved by imparting to the solidifying casting an angular acceleration. This angular acceleration is obtained by rotating the solidifying casting first in one direction and then the other. This results in a continuous angular acceleration which varys also in sign and magnitude. Typical commercially important metals upon which this invention has been successfully practiced are gray irons and heat resistant super alloys based upon iron, nickel or cobalt. This invention is particularly applicable to castings whose surfaces are surfaces of revolution.

The velocity of rotation employed in the current proce'ss is not to be confused with the much greater velocity of rotation conventionally employed in the'process known as centrifugal casting. Such a conventional centrifugal casting process is taught by a patent issued Oct. 27, 1942 to S. M. Stoody et al. as 2,299,860. This patent teaches the production of an aircraft supercharger wheel from heat and corrosion resistant alloys and of approximately the same size as described later in the current invention. Stoody states in line 46 of page 3 that the rate of rotation is 1,500 R.P.M. This is to be contrasted with the 100 R.P.M. which has been found to be adequate for the execution of Applicants process. Inasmuch as the centrifugal forces vary as the square of the peripheral speed divided by the radius, the Stoody process which is typical of commercial practice would subject the metal to stresses 225 times as greatas those employed by Applicants.

This invention was carried out by casting the various metals into refractory molds supported upon a rotatable metal plate. This plate is driven by a reversible electric motor arranged to rotate the mold supporting plate at 120 R.P.M. when energized and permitted to come to full speed.

The oscillatory motion was obtained by reversing the electric motor each 4 seconds. This time interval is too brief to permit the metal plate to reach the full equilibrium speed of 120 R.P.M. and caused it to reverse in V torque when a speed of only about 100 R.P.M. had been reached. I

The tremendous commercial importance of gray iron made it a logical candidate upon which to demonstrate this invention. To this end FIGS. 1, 2 and 3 have been presented showing a conventional gray iron composition at varying degrees of magnification after casting during oscillation.

' FIG. 1 is a conventional gray iron consisting essentially of iron alloyed with 3.3 percent carbon and 3.1

percent silicon. The magnification in FIG. 1 is only 1.5X but the radical change produced by oscillation is readily apparent.

FIG. 2 is the same alloy as FIG. 1 with the magnification increased to 30X. There is a pronounced refinement of the flake structure in the oscillated ingot as compared to the conventionally cast ingot.

FIG. 3 is a logical extension of the showings of FIGS. 1 and 2 and demonstrates the effect of oscillation upon a remelted conventional nodular iron. The large eutectic cells in the conventionally cast ingot are reoriented in the oscillated ingot. The magnification is 20X.

FIG. 4 constitutes a graphic presentation of the effect of oscillation upon the graphite distribution in a gray cast iron containing 4.1 percent carbon and 1.6 percent silicon. This drawing contains three curves, one each for the static mode of casting, for the rotated casting and for the oscillated casting. The abscissae represent the distance from the edge of the casting and the ordinates the volume percent graphite.

FIG. 5 is analagous to FIG. 4 except that it is directed to two nickel base super alloys known to the trade as TRW VI A alloy and Ford 406 alloy. The chemistry of these alloys is as follows: Y

TRW VI A Ford 406 6.1 Cr 6.0 Cr 7.5 Co 10.0 Co 2.0 Mo 1.0 M0 5.8 W 8.5 W 5.4 A1 4.5 Al 1.0 Ti 2.0 Ti 0.5 Nb 2.0 Nb 9.0 Ta 6.0 Ta 0.13 C 0.13 C 0.015 B 0.0l5 B 0.1 Zr 0.] Zr 0.5 Re

The pronounced effect of the oscillation upon the average percentage of primary gamma prime is readily apparent.

We claim as-our invention:

1. In a method for controlling micro-structural phase concentrations in centrifugally cast metallic material, the steps of: subjecting a molten mass of said material to oscillations at least equal to about 4 seconds in period determined from the start of motion in one direction for each oscillation to the completion of motion in said one direction, the speedof said mass varying continuously during each oscillation and attaining an angular speed no greater than about rpm. near the terminal portion of each oscillatory movement.

2. The method as in claim 1, in which the molten mass is comprised of iron alloyed with at least 3.3 percent carbon and about 1.6 percent silicon, the oscillatory movement of said mass producing a generally uniform distribution of a graphite phase in cast iron, the uniform distribution being viewed from the outer to the most inner regions of the casting.

3. The method as in claim 1, in which the molten mass is comprised of a nickel base super alloy comprising about 6% Cr, 7% Co, 2% M0, 5.4% Al, 9.0% Ta, 5.8% W, the oscillatory movement of said mass producing a casting in which the primary gamma prime is generally uniform throughout the entire casting with a cross-sectional variation no greater than 1 percent.

4. The method as in claim 1, in which the molten mass is comprised of a nickel based alloy having at least 6% C, about 10% Co and about 1% M0, 8.5% W, 4.5% Al, the oscillatory movement of said mass producing a casting in which a primary gamma prime phase is predominantly concentrated at a mid-radial region of said casting, the primary gamma prime phasehaving a concentration at said mid-radial region at least 1 percent greater than the concentration at either the innermost or outermost region of said casting.

8 I. l i t 

1. In a method for controlling micro-structural phase concentrations in centrifugally cast metallic material, the steps of: subjecting a molten mass of said material to oscillations at least equal to about 4 seconds in period determined from the start of motion in one direction for each oscillation to the completion of motion in said one direction, the speed of said mass varying continuously during each oscillation and attaining an angular speed no greater than about 100 r.p.m. near the terminal portion of each oscillatory movement.
 2. The method as in claim 1, in which the molten mass is comprised of iron alloyed with at least 3.3 percent carbon and about 1.6 percent silicon, the oscillatory movement of said mass producing a generally uniform distribution of a graphite phase in cast iron, the uniform distribution being viewed from the outer to the most inner regions of the casting.
 3. The method as in claim 1, in which the molten mass is comprised of a nickel base super alloy comprising about 6% Cr, 7% Co, 2% Mo, 5.4% Al, 9.0% Ta, 5.8% W, the oscillatory movement of said mass producing a casting in which the primary gamma prime is generally uniform throughout the entire casting with a cross-sectional variation no greater than 1 percent.
 4. The method as in claim 1, in which the molten mass is comprised of a nickel based alloy having at least 6% C, about 10% Co and about 1% Mo, 8.5% W, 4.5% Al, the oscillatory movement of said mass producing a casting in which a primary gamma prime phase is predominantly concentrated at a mid-radial region of said casting, the primary gamma prime phase having a concentration at said mid-radial region at least 1 percent greater than the concentration at either the innermost or outermost region of said casting. 